Pressure fluid controlled reciprocating mechanism

ABSTRACT

A fluid controlled mechanism that includes a reciprocating member that is actuated by stored potential energy, with the member as it moves from a second to a first position providing usable kinetic energy. Two moving parts of the mechanism so distribute fluid at three different pressure levels on a plurality of different sized areas that said member alternately and automatically moves between said first and second positions. The stored potential area may result from a pressurized gas head, a spring, weight means, or the like. The fluid at one of the three pressure levels may be air at the ambient pressure if desired. The mechanism may be employed for such diverse purposes as a high velocity energy generator in an impact or demolition tool, as well as a reciprocating power source in hammers, chisels and spades, and also as a power source for pumps, boosters, sickle bars, concrete screeds and the like.

United States Patent Densmore [54] PRESSURE FLUID CONTROLLEDRECIPROCATING MECHANISM [72] Inventor: Richard M. Densmore, South Gate,

Calif.

[73] Assignee: W. J. Savage Co., Inc., Knoxville,

Tenn.

- [22] Filed: Feb. 1, 1971 [21] Appl. No.: 111,359

[52] US. Cl. ..91/25, 91/165, 91/235,

[51] Int. Cl. ..Fl5b 15/22, F01b 7/18, F011 17/00 [58] Field of Search...91/232, 235, 276, 321, 328,

Primary ExaminerPaul E. Maslousky Attorney-William C. Babcock ABSTRACT Afluid controlled mechanism that includes a reciprocating member that isactuated by stored potential energy, with the member as it moves from asecond to a first position providing usable kinetic energy. Two movingparts of the mechanism so distribute fluid at three different pressurelevels on a plurality of different sized areas that said member a1-temately and automatically moves between said first and secondpositions. The stored potential area may result from a pressurized gashead, a spring, weight means, or the like. The fluid at one of the threepressure levels may be air at the ambient pressure if desired.

The mechanism may be employed for such diverse 9 Claims, 7 DrawingFigures PRESSURE FLUID CONTROLLED RECIPROCATING MECHANISM BACKGROUND OFTHE INVENTION 1 Field of the Invention Pressure fluid controlledreciprocating mechanism.

2. Description of the Prior Art In the past, various types ofreciprocating mechanisms have been developed in which the actuationthereof is a result of hydraulic fluid supplied to the being in sealingcontact. Just after the second reciprocating member has reached thesecond position, the continued flow of hydraulic fluid at the firstpressure results in the sleeve moving in a direction to break the sealbetween the valve seat and valve member to momentarily over 'the firstpressure in the mechanism to allow the inert gas charge or other sourceof potential energy to move the reciprocating member from the second tothe first position.

A major object of the present invention is to provide a fluid controlledmechanism that has but two movable parts that so control fluid at threedifferent pressures that a reciprocating member that is at all timessubjected to potential energy generating means alternately mechanism, inwhich the reciprocating member moves alternately between first andsecond positions, and in moving from the second to the first position isenergized by a potential source of energy such as a gas head, spring orweight that forms a part of the mechanism. Two moving parts only, thatform a part of the mechanism, so direct fluid at three differentpressure levels on areas of various sizes situated within the mechanismto cause the actuation of the reciprocating member. The fluid employedis preferably oil that is supplied by a conventional system, with a backpressure being maintained at the egress by conventional means in the oilreturn system to the reservoir. This combination together with a vent tothe atmosphere supplies fluid pressure at three different levels, withonly one input source of hydraulic fluid being required. The kineticenergy supplied by the reciprocating member as it moves from a second toa first position is preferably provided by a precharged inert gaschamber. High energy developing sources may be stored in such a chamberto occupy a relatively small amount of space and with a low weightfactor.

SUMMARY OF THE INVENTION A fluid controlled mechanism that includes ahousing in which a reciprocating member is movably supported and isoperatively associated with a source of stored potential energy that atall times tends to move said member from a second to a first position.The reciprocating member has a valve member extending outwardlytherefrom, and the valve member capable of effecting a seal with a valveseat that forms a part of a sleeve slidably movable in the mechanism.Fluid at first and second pressures are supplied to the interior of thehousing with said first pressure being substantially higher than thesecond pressure. The interior of the housing is vented to the atmosphereor if desired to a source of hydraulic fluid at lower pressure. Theventing of the interior of the mechanism to the atmosphere provides thethird fluid pressure level, which is less than that of the pressure onthe first and second fluids.

The potential energy developing means that moves the reciprocatingmember from the second to the first position is inert gas at asubstantially high pressure, but a pressure lower than that exerted onthe first hydraulic fluid. After the reciprocating member has moved froma second to a first position, the slidable sleeve and reciprocatingmember move in unison towards the second position, with the valve memberand valve seat and automatically moves between first and secondpositions to produce useful work.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal crosssectional view of the mechanism, with the reciprocating member in asecond position, and the valve seat supporting sleeve in sealing contactwith the valve member;

FIG. 2 is a transverse cross sectional view of the device taken on theline 2-2 of FIG. 1;

FIG. 3 is a second transverse cross sectional view of the device takenon the line 3-3 of FIG. 1;

FIG. 4 is a second longitudinal cross sectional view of the device withthe valve member and valve seat separated and the reciprocating memberjust starting to move to the left from the second position as a resultof the gas head in the device;

FIG. 5 is a third longitudinal cross sectional view of the device withthe reciprocating member having moved to a first position to complete awork producing stroke, and the valve seat and valve member still beingseparated;

FIG. 6 is a fourth longitudinal cross sectional view of the device, withthe reciprocating member in the second position, and the valve seat andvalve member in sealing contact with one another; and

FIG. 7 is a diagrammatic atic view of the fluid pressure producingassembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT The fluid controlled mechanism Mas may be seen in FIGS. 1 to 6 inclusive includes a housing assembly Bthat slidably supports an elongate member C that reciprocates betweenfirst and second longitudinally spaced positions. Member C is at alltimes urged to the first position shown in FIG. 6 by potential energyproviding means D.

Housing assembly B slidably supports a sleeve E within the interiorthereof. Sleeve E includes a valve seat F that may be sealingly engagedby a valve member G that is a part of member C or mounted thereon.

Housing assembly B includes a side wall 18 that has first and secondlongitudinally spaced bosses 20 and 22 formed as a part thereof. Bosses20 and 22 have transverse first and second fluid passages 20a and 22aextending therethrough. First passage 20a is in communication with afirst conduit 24 that is supplied with a first fluid H-l, preferablyhydraulic oil, at a constant rate and at a first pressure P-l byconventional means shown in FIG. 7.

The second fluid passage 22a is connected to a second conduit 26 thatsupplies a second fluid I-I-2, preferably hydraulic oil, that ismaintained at a second back pressure P-2 by conventional means shown inFIG. 7. The first and second fluids H-1 and I-I-2 must both be alike,either liquids or gases. The side wall 18 has a third transverse passage28 therein and as shown in FIG. 6 thence the interior housing assembly Bto the ambient atmosphere which is at a third pressure P-3.

In detail, the side wall 18 is preferably a cylindrical shell as shownin FIG. 3, and has a first open end portion 20 on which threads 32 areformed. A second end of side wall 18 is closed by an end piece 34 thathas a fourth fluid passage 36 therein. A valve 38 is secured in a fixedposition to end piece 34 and is in communication with fourth fluidpassage 36. The valve 38 permits an .inert gas, such as nitrogen underpressure, to be discharged into housing assembly B to supply thepotential energy providing means D.

The side-wall 18 has a transverse partition 40 therein that isintermediately located between end piece 34 and first end portion 30.Partition 40 has a longitudinal opening 42 therein in which the righthand end portion of reciprocating member C is slidably supported. Theside wall 18, end piece 34, partition 40 and member C cooperate todefine a compartment 44 in which an inert gas such as nitrogen iscontained under a pressure P-4. The pressurized gas constitutes thepotential energy providing means D in the mechanism M as illustrated.The right hand portion of member C as viewed in FIG. has a longitudinalrecess 46 therein that forms an extension of compartment 44. If desired,the potential energy providing means D may be a mechanical element, suchas a compressed spring, or a weight if the mechanism is operated in avertical position.

The forward end of recess 46 is defined by a transverse face 48. MemberC terminates on the right hand end thereof as viewed in FIG. 5 in a ringshaped face 50. Housing assembly B further includes an internallythreaded cap 52 that engages threads 32 as shown in FIG. 5. The cap 52has a. longitudinal bore 54 and counterbore 56 therein that define abody shoulder 58 at their junction.

Member C has a first portion 60 that is of less transverse cross sectionthan a second portion 62 thereof. The portions 60 and 62 define acircumferentially extending surface 64 that acts as a stop when itcontacts body shoulder 58 as shown in FIG. 5.

A generally cylindrical plug 66 is provided that is disposed in theforward portion of shell 18 as viewed in FIG. 5. Plug 66 has alongitudinal bore 68 therein that slidably supports member portion 62. Acircular flange 71 extends outwardly from plug 66 and is gripped betweenfirst end portion 30 and the interior surface 73 of cap 52 as shown inFIG. 5.

The outer surface of plug 66 and interior surface of shell 18 cooperateto define an annulus shaped space 73 therebetween in which the sleeve Eis longitudinally movable when the sleeve has the interior surface 11thereof in sliding engagement with plug 66.

Valve member G is of ring-shape configuration and is defined by an outercylindrical surface 12, a forward ring-shaped surface 12a, and arearward ring-shaped surface 12b. The second member portion 62 isdefined by a first cylindrical surface 13, and a third portion 62a ofthe member C rearwardly of valve member G as viewed in FIG. 5 by asecond cylindrical surface 16. In the drawings, the first and secondsurfaces 13 and 16 are shown as of the same diameter but thisconstruction is not required. A longitudinal phantom line 64 is extendedrearwardly in FIG. 6 from surface 11 to show that the diameter ofsurface 12 is less than the interior diameter of sleeve E.

The sleeve E as may best be seen in FIG. 6 has an internally,circumferentially extending recess 68 formed therein that on the endsthereof are defined by surfaces 68a and 68b. The surface 68b is definedon the forward surface of the valve seat F. The valve seat F as shown inFIGS. 5 and 6 has an internal cylindrical surface that is radiallyspaced from the surface 16. The rearward end of the valve seat F isdefined by an annulus-shaped surface 72. The valve member G has thesurface 12b thereof, as may best be seen in FIGS. 5 and 6, extendinginwardly and forwardly. As a result only a narrow ring-shaped portion ofthe valve-member G is in sealing contact with the valve seat F when thereciprocating member is disposed as shown in FIG. 6.

The cylindrical sidewall 18 has two longitudinally spaced internallypositioned grooves 74 and 76 formed therein that are occupied byresilient sealing rings 78 and 80 that are at all times in pressuresealing contact with the exterior surface of the sleeve F. The plug 66has inner and outer circumferentially extending grooves 82 and 84 formedtherein that are occupied by resilient sealing rings 86 and 88. Thesealing ring 86 is at all times in slidable sealing contact with thesurface 13 of reciprocating member C. The sealing ring 88 is likewise atall times in slidable sealing contact with the interior surface 11 ofsleeve E as may be seen in FIGS. 5 and 6. Partition 40 has acircumferentially extending groove 90 projecting outwardly from theopening 42, and this groove being occupied by a resilient sealing ring92 that is at all times in slidable sealing contact with the surface 16of reciprocating member C. A transverse port 94 is formed in therearward portion of the reciprocating member C as viewed in FIG. 5 to atall times maintain communication between the compartment 44 and recess46, particularly when the reciprocating member is in the second positionillustrated in FIG. 1.

The source for the hydraulic fluids l-I-l and H-2 is shown in FIG. 7. Aprime mover 96 is provided that by rotatable transmission means 90drives a pump 100. The pump 100 has the suction line 102 thereofconnected to an oil reservoir 104. The discharge line 106 of the pump isconnected to a constant pressure outlet valve 108 that dischargeshydraulic fluid l-I-l through a conduit 24 to the bore 20 on shell 18when mechanism M is operating. Hydraulic fluid flowing to the conduit106 flows through the valve 108 and is returned to the reservoir 104 bya conduit 110 when mechanism M is not operating. The conduit 26 isconnected to the boss 22 and extends to a tee or other suitable fittingl 12 that is connected by a conduit -1 14 to an accumulator 116. Thefitting 112 is also connected to a pressure relief valve 118, whichvalve has the outlet therefrom connected to a conduit 110 by a conduit120. The accumulator 116 and valve 118 cooperate to maintain a backpressure P-2 on the fluid H-2.

The operation of the device is as follows. In describing the operationof the mechanism M it is convenient to consider certain componentsthereof as defining particular areas of different magnitude that areexposed to the action of the fluids H-l and H-2. These fluids willnormally be identical in composition, and are only referred to by thenotation H-1 and l-I-2 to clarify the operation of the device. Theforward face 12a of the valve member G, between the surface 12 and 13,defines a ring shaped area that is referred to in the followingdescription by the notation A-l.

A ring-shaped area A-2 is defined on the forward face of the valve seatG that is a projection of the cylindrical surface 12 as well as thephantom line extension 64 thereon. A ring-shaped portion of the surface72 on the valve member F between the surface and the phantom line 64 isreferred to as area A-3.

The ring-shaped face 50 and the face 48 on the rearward end of thereciprocating member C cooperate to provide an area A-4 that is exposedto the pressure P-4 of the gas head in the compartment D. The shape andsize of the valve member G may vary from that shown in FIGS. 5 and 6,but increasing the depth of the valve member will only result in asubtraction of the opposing forces produced by the fluid I-I-2 atpressure P-2 and add a like force to be exerted on the sleeve E at thevalve seat F thereon. When the prime mover 96 is operating, the pump 100is driven and fluid H-l is supplied to a circumferentially extendingrecess 122 in the interior of the shell 18 as shown in FIG. 5, whichrecess is situated between the sealing rings 74 and 76. The sleeve E hasa number of circumferentially spaced radially extending ports 124 formedtherein as shown in FIGS. 1 and 2 that are at all times in communicationwith the recess 122 and areas A-1 and A-2. When no hydraulic fluid H-lis being furnished at a pressure P-l to the conduit 24, the gas head inthe compartment 44 and recess 46 will exert a force on the area A-4 thatdisposes the reciprocating member C in the first position shown in FIG.6.

The pressures involved in actuating the mechanism M are substantiallydifferent in magnitude. In practice it has been found to operatesatisfactorily when the pressure P-l is 1,000 p.s.i., and the pressureP-2 is 150 p.s.i. The pressure P-3 may be that of the ambientatmosphere, and the pressure P-4, the precharge of the nitrogen in thecompartment 44 and 46, may be 765 p.s.i. These pressures are statedmerely for the purpose of illustration, and in no sense as a limitationon the pressures involved in the actuation of the device. It will beapparent that either a negative or positive pressure P-3 may beprovided, and that the negative pressure would be supplied by a vacuumproducing device, and the positive pressure by a body of oil that ismaintained at a low pressure. Variations in the magnitude of the fourpressures involved will obviously have an appreciable effect on theforce at which the member C is reciprocated, and the work produced bythe member C as it moves from the second position shown in FIG. 1 to thefirst position illustrated in FIG. 6.

In FIG. 6, when the reciprocating member C is in the second position itwill be seen that a force A-3 times P- 2 is exerted on the sleeve Etending to move it to the left, while a force A-2 times P-l minus P-2tends to move the sleeve to the right. The force P-3 is that of thesleeve E is alternately moved longitudinally in the mechanism M. Also,to hold the valve member G in sealing contact with the valve seat F, theforce A-3 times P-2 must be greater than the force A-2 times P-l minusP-2. The forces acting on the valve member F are A-4 times P-4 that tendto move the reciprocating member'C to the left, and a force A-l timesP-l tends to move the reciprocating member C to the right. Here A-ltimes P-l must be greater than A-4 times P-4, plus the forces previouslydescribed, since the reciprocating member C must move to the rightagainst these forces too..Also, opposing this movement is P-2 times thearea of the surface 12b on the valve member G between the surface 12 and16.

The above described forces result in the valve member C moving from thefirst position shown in FIG. 6 to the second position illustrated inFIG. 1. When the valve member C is stopped due to the surface 50contacting the interior surface of the end piece 34, the pressure P-lincreases by demand so that the force A-3 times P-2 on valve seat F isless than the pressure A-2 times P-l minus P-2 thereon, and the sealbetween the valve member G and valve seat F is broken by relativemovement of the valve seat to the valve member. The reciprocating memberC is then released with a force that is equal to the area A-4 times thepressure P-4. Since there is little or no change in displacement in thehousing assembly B during this operation, the resistance to thismovement of the reciprocating member C to the left is that of thefriction of the moving parts and seals. Accordingly, there is highvelocity movement of the reciprocating member C to the left that may beutilized to produce useful work or impact on a tool mounted on housingassembly B. However, regardless of how the reciprocating member C isstopped, the action is the same for returning the reciprocating member Cfrom the first position shown in FIG. 6 to the second positionillustrated in FIG. 1. In FIG. 5, the reciprocating member C is depictedas being stopped by the surface 64 thereof contacting the surface 58 ofthe cap 52.

The force acting on the valve seat F when the sleeve E is moving to theleft is A-3 times P-2 minus A-2 times P-l, and the velocity of movementis controlled by rate of input of liquid H-l into housing assembly B.The continued movement of the sleeve E to the left results in thepositioning of the reciprocating member C as shown in FIG. 6. The energyproviding means D is illus trated in the drawing as being a precharge ofinert gas such as nitrogen or the like that is admitted into thecompartment 44 and recess 46 by use of the valve 38, which may belocated in any convenient portion of the rearward part of the housingassembly B so long as it is to the right of the partition 40 as viewedin FIGS. 5 and 6. The reciprocating member C may be used for any desiredwork producing purpose. For instance, if desired, an internally threadedtool T may be mounted on threads 126 formed on the cap 52 and theextreme left end of the reciprocating member C (not shown) impacting onthe interior of the tool to accomplish a desired result.

The use and operation of the mechanism has been previously described indetail and need not be repeated.

lclaim:

1. In a work-producing mechanism having a hollow housing defined byfirst and second ends and connecting sidewall means and an elongate workproducing member slidably supported in said housing, with a firstportion of said member projecting outwardly through an opening in saidfirst end, the improvement for causing said member to automaticallyreciprocate between first and second positions in said housing by first,second and third fluids, said first fluid being pressurized by meansexterior of said housing that is in communication with .the interior ofsaid housing through a first passage in said sidewall, said means ondemand supplying said first fluid to said housing at a first pressure,back'pressure means that maintain said second fluid in said housinguntil a second pressure is reached on said second fluid whereupon saidsecond fluid is discharged from saidhousing, said second pressure beingless'than said first pressure, said improvement comprising:

a. potential energy generating means that at all times tend to maintainsaid member in a first position where said first portion is of maximumlength;

. a cylindrical sleeve slidably supported for longitudinal movement insaid housing, said sleeve having first and second ends and an innercylindrical surface, with said sleeve extending around said member insaid housing, and said sleeve having at least one transverse openingtherein that is at all times in communication with said first fluidpassage;

c. a ring-shaped valve member that projects outwardly from said memberand is at all times disposed in said sleeve and in communication withsaid opening therein;

-d. a ring-shaped valve seat that extends inwardly from said second endof said sleeve, with the external diameter of said valve member greaterthan the internal diameter of said seat, and said valve member and valveseat when said elongate member is in said first position capable ofbeing in sealing contact; I

e. first means for maintaining said third fluid at a third pressure incommunication with said first end of said sleeve, said third pressurebeing less than said first pressure, said first fluid after said memberhas moved to said first position and said valve member and valve seatare in sealing contact exerting a sufficient force on first and secondringshaped areas defined on said valve member and valve seat as to movesaid elongate member and valve member towards said second positionagainst the force offered by said potential energy generating means andthe force exerted by said second fluid on a third ring-shaped areadefined on said valve seat, with said force exerted by said second fluidon said third area being greater than the force exerted by said firstfluid on said second area as the movement of said elongate membertowards said second position takes place to maintain said valve memberand valve seat in sealing contact, and the force exerted by said firstfluid on said second area being greater than the force exerted by saidsecond fluid on said third area after said second position is reached tobreak the seal between said valve member and valve seat to momentarilyallow the pressure on said first fluid to drop to said second pressurewhereupon said potential energy generating means drives said I memberfrom said second to said first position at high velocity, with saidsleeve and valve seat thereafter moving towards said first end for saidvalve seat to seal with said valve member due to the force exerted bysaid second fluid on said third area being greater than the forceexerted by said first fluid on said valve seat and the force exerted bysaid third fluid on said first end of said sleeve.

2. A work producing mechanism as defined in claim 1 in which said firstand second fluids are first and second hydraulic liquids and said thirdfluid is air at the ambient atmosphere.

3. A work producing mechanism as defined in claim 1 in which said firstand second fluids are first and second hydraulic liquids and said thirdfluid is maintained at a third pressure other than that of the ambientatmosphere and at a magnitude less than that of said second pressure.

' 4. A work producing mechanism as defined in claim 1 in which saidpotential energy providing means is a charge of pressurized gas sooperatively associated with said housing assembly as to all times tendto move said reciprocating member from said second to said firstposition.

5. A work producing mechanism as defined in claim 4 which in additionincludes:

f. a transverse partition that extends across said sidewall meansintermediate said first and second ends,said partition having an openingtherein axially aligned with said opening in said first end, saidopening in said partition slidably engaged by said reciprocating member,and said second end, partition, and portions of said reciprocatingmember and sidewall means cooperating to define a compartment in whichsaid charge of pressurized gas is contained.

6. A work producing mechanism as defined in claim 5 in which saidelongate member has a longitudinal recess therein that is at all timesin communication with said compartment and provides an extensionthereof.

7. A work producing mechanism as defined in claim 1 which in additionincludes: 7

g. an impact actuated tool mounted on said housing assembly tointermittently receive blows from said reciprocating member as saidreciprocating member moves to said second position.

8. A work producing mechanism as defined in claim 1 which in additionincludes:

f. a cylindrical plug that extends inwardly from said first end andslidably engages the interior surface of said sleeve and the exteriorsurface of said elongate member, with said plug, first end of saidhousing, a portion of the interior surface of said sidewall means andsaid first end of said sleeve cooperating to define an annulus-shapedconfined space of variable volume in which said third fluid iscontained, and said confined space at all times being in communicationwith a third transverse fluid passage formed in said sidewall means, andsaid third fluid being air at ambient pressure.

9. A work producing mechanism as defined in claim 8 which in additionincludes:

g. a plurality of resilient sealing rings mounted in transversecircumferential grooves in the interior

1. In a work-producing mechanism having a hollow housing defined byfirst and second ends and connecting sidewall means and an elongate workproducing member slidably supported in said housing, with a firstportion of said member projecting outwardly through an opening in saidfirst end, the improvement for causing said member to automaticallyreciprocate between first and second positions in said housing by first,second and third fluids, said first fluid being pressurized by meansexterior of said housing that is in communication with the interior ofsaid housing through a first passage in said sidewall, said means ondemand supplying said first fluid to said housing at a first pressure,back pressure means that maintain said second fluid in said housinguntil a second pressure is reached on said second fluid whereupon saidsecond fluid is discharged from said housing, said second pressure beingless than said first pressure, said improvement comprising: a. potentialenergy generating means that at all times tend to maintain said memberin a first position where said first portion is of maximum length; b. acylindrical sleeve slidably supported for longitudinal movement in saidhousing, said sleeve having first and second ends and an innercylindrical surface, with said sleeve extending around said member insaid housing, and said sleeve having at least one transverse openingtherein that is at all times in communication with said first fluidpassage; c. a ring-shaped valve member that projects outwardly from saidmember and is at all times disposed in said sleeve and in communicationwith said opening therein; d. a ring-shaped valve seat that extendsinwardly from said second end of said sleeve, with the external diameterof said valve member greater than the internal diameter of said seat,and said valve member and valve seat when said elongate member is insaid first position capable of being in sealing contact; e. first meansfor maintaining said third fluid at a third pressure in communicationwith said first end of said sleeve, said third pressure being less thansaid first pressure, said first fluid after said member has moved tosaid first position and said valve member and valve seat are in sealingcontact exerTing a sufficient force on first and second ring-shapedareas defined on said valve member and valve seat as to move saidelongate member and valve member towards said second position againstthe force offered by said potential energy generating means and theforce exerted by said second fluid on a third ring-shaped area definedon said valve seat, with said force exerted by said second fluid on saidthird area being greater than the force exerted by said first fluid onsaid second area as the movement of said elongate member towards saidsecond position takes place to maintain said valve member and valve seatin sealing contact, and the force exerted by said first fluid on saidsecond area being greater than the force exerted by said second fluid onsaid third area after said second position is reached to break the sealbetween said valve member and valve seat to momentarily allow thepressure on said first fluid to drop to said second pressure whereuponsaid potential energy generating means drives said member from saidsecond to said first position at high velocity, with said sleeve andvalve seat thereafter moving towards said first end for said valve seatto seal with said valve member due to the force exerted by said secondfluid on said third area being greater than the force exerted by saidfirst fluid on said valve seat and the force exerted by said third fluidon said first end of said sleeve.
 2. A work producing mechanism asdefined in claim 1 in which said first and second fluids are first andsecond hydraulic liquids and said third fluid is air at the ambientatmosphere.
 3. A work producing mechanism as defined in claim 1 in whichsaid first and second fluids are first and second hydraulic liquids andsaid third fluid is maintained at a third pressure other than that ofthe ambient atmosphere and at a magnitude less than that of said secondpressure.
 4. A work producing mechanism as defined in claim 1 in whichsaid potential energy providing means is a charge of pressurized gas sooperatively associated with said housing assembly as to all times tendto move said reciprocating member from said second to said firstposition.
 5. A work producing mechanism as defined in claim 4 which inaddition includes: f. a transverse partition that extends across saidsidewall means intermediate said first and second ends, said partitionhaving an opening therein axially aligned with said opening in saidfirst end, said opening in said partition slidably engaged by saidreciprocating member, and said second end, partition, and portions ofsaid reciprocating member and sidewall means cooperating to define acompartment in which said charge of pressurized gas is contained.
 6. Awork producing mechanism as defined in claim 5 in which said elongatemember has a longitudinal recess therein that is at all times incommunication with said compartment and provides an extension thereof.7. A work producing mechanism as defined in claim 1 which in additionincludes: g. an impact actuated tool mounted on said housing assembly tointermittently receive blows from said reciprocating member as saidreciprocating member moves to said second position.
 8. A work producingmechanism as defined in claim 1 which in addition includes: f. acylindrical plug that extends inwardly from said first end and slidablyengages the interior surface of said sleeve and the exterior surface ofsaid elongate member, with said plug, first end of said housing, aportion of the interior surface of said sidewall means and said firstend of said sleeve cooperating to define an annulus-shaped confinedspace of variable volume in which said third fluid is contained, andsaid confined space at all times being in communication with a thirdtransverse fluid passage formed in said sidewall means, and said thirdfluid being air at ambient pressure.
 9. A work producing mechanism asdefined in claim 8 which in addition includes: g. a plurality ofresilient sealing rings mountEd in transverse circumferential grooves inthe interior surface of said sidewall means and the exterior andinterior surfaces of said plug to prevent axial flow of said first fluidbetween said sidewall means and sleeve, the interior surface of saidsleeve and the exterior surface of said plug, and the interior surfaceof said plug and exterior surface of said reciprocating member.